Process for the manufacture of electrolytic devices



y 1941- P. ROBINSON ETAL 2.249,091

PROCESS FOR THE MANUFACTURE OF ELECTROLYTIC DEVICES Filed June 15, 1937 1N VENTORS PRESTON ROBINSON &

BY MATHEW NAZZEWSKI C'flz/ 91 gonna,

AH FORNEYS In fact, creepage of the electrolyte frequently Patented July 15, 1941 UNITED STATES PATENT OFFICE PROCESS FOR THE MANUFACTURE OF ELECTROLYTIC DEVICES Preston Robinson, Wllliamstown, and Mathew Nazzewski, North Adams, Mass assignors to Sprague Specialties Company, North Adams, Mass, a corporation of Massachusetts Application June 15, 1937, Serial No. 148,398

1 Claim. (01. 154-2) The present invention relates to electrolytic pansion of the bore, thus permitting the riser devices and more particularly to improvements to be passed through same. However, after the in the construction of electrolytic condensers. swelling liquid has evaporated, the bore tends In various types of electrolytic devices, for into close up to its original diameter, thereby constance, electrolytic condensers, a liquid and air- 5 stantly exerting a very high pressure on the tight sealing of the device is of primary imporelectrode-riser and providing between the plug tance. Not only is this required to forestall the and the riser for a very tight fit-of permanent spilling of the electrolyte but also to prevent the character. salt dissolved in the electrolyte from creeping Referring to the drawing which forms part of through leaks which may occur in the joints of the specification: such devices, a phenomenon which is character- Figure l is a sectional elevation of an electroistic of all electrolytic apparatus and which is lytic condenser embodying the invention; due to the salt separating out of the solution. Fig. 2 is a perspective view of that end of the condenser of Fig. 1 which carries the plug of takes place through joints which are seemingly the invention; impermeable to the liquid electrolyte. In view Fig. 3 is a sectional side-elevation of the conof the above and because of the importance of denser portion of Fig.2; preventing contamination of the electrolyte by Fig. 4 is an enlarged schematic drawing indiimpurities which may enter through such leaks, eating the principle of the invention, and showthe requirement of perfect sealing of such devices ing the rubber plug before and after its swelling. is evident. Referring to the drawing, the condenser shown The main difiiculty in obtaining a liquid and therein comprises a cylindrical metallic container air tight seal in electrolytic condensers and simin, which preferably constitutes its cathode and ilar devices is due to the fact that outside elecwhich may be either of film-forming or nontrical connection has to be made with the elecfi or metal. The Container 10 is p trode or electrodes within the device and the vided with a reduced tubular extension i2, joints between such connection and the sealing threaded at 20 and extending into a further remember, unless very expensive constructions are duced tubular portion 2|. used, are likely to develop leaks. The anode assembly 28 as shown consists oi For example, in a widely used construction a corrugated thin foil 29 of aluminum or other for electrolytic condensers, a plug of soft rubber film-forming metal, having the shape of an acor similar resilient gasket material is provided cordion pleating, which is suitably secured, for through which passes a so-called electrode-riser, example by means of welding or by rivets, to which serves for the support and electrical conan anode riser 30. The riser 30 consists of a nection of the electrode. straight rod of rectangular or cylindrical shape To obtain a tight fit between the riser and and projects with its end 34 beyond the conthe plug, a hole which is slightly smaller than tainer portion 2!. The anode riser 30 may be of that of the riser is provided in the plug. While aluminum or of other, preferably film forming, this together with the crimping of the plug gives metal.

a substantially tight joint, still such a construc- The top of the container is provided with a tion frequently permits a certain amount of crowned metal cap l6, which fits into the concreepage and loss of the electrolyte during the tainer end i3. A vent gasket H- of suitable maoperation of the condenser and therefore is not terlal, for example of wax-impregnated cloth, is a satisfactory solution of the problem. interposed between the container l0 and thecap The object of the present invention is to overcome the above difficulty and to provide an al- N interposed, is crimped over a rim provided ways reliable and permanently tight fit between on the container ID. the sealing plug and the electrode-riser passing Interposed between the container in and the through same. anode assembly 28 is an insulator, for instance,

In accordance with the invention, the plug is a thin hard rubber cylinder 32 provided with made of vulcanized rubber and after having been perforations 33, to prevent the anode foil 29 provided with a bore which is considerably smallfrom contacting with the container I0. er than one which would permit the electrode- The threads 20 are adapted to receive a nut riser to pass through same, is subjected to a (not shown) by means of which the condenser swelling process, which temporarily causes exmay be attached to asuitable base.

45 IS. The free edge of the cap i6, with the gasket large in diameter.

The extension 2| has preferably the same in side diameter as the extension l2, so that the two form a common bore 22, the wall thickness of the extension 2| is however preferably much less than that of the extension I2.

Placed in the bore 22 is a tightly fitting plug 25 preferably of semi-hard vulcanized rubber through which passes the anode-riser II.

In accordance with the invention the vulcanized rubber plug 25 is provided with a bore the cross-section of which is considerably less than that of the anode-riser. For example, if a round anode-riser is used having a diameter of .125 inch, the diameter of the hole should be about .060 to .070 inch.

We have found that if such a plug of vulcanized rubber is put into a solvent of the type of chlorobenzene, benzene, gasoline, dibutylamine, ether, and the like, the rubber swells and occupies a volume which is considerably in excess of its original volume, whereby the relative amounts of swelling depend on the solvent, the highest swelling being obtainable with chloro-benzene and benzene. It should be noted that such swelling takes place primarily at the surface of the rubber and that generally the greater portion of the rubber remains unchanged.

We have furthermore found that if a vulcanized rubber stopper is perforated with a fine clean-cut hole and the rubber is put into a solvent of the above type, the swelling takes place in such a manner that instead of the fine hole being blocked up by the swelling of the rubber as would be expected, the hole is caused to actually en- What apparently takes place is that the increased volume of the swelled rubber pushes out the ends of the hole.

If now a metal rod such as the riser 30 is forced into the stopper, so that it makes a fairly tight fit in the enlarged hole of the swelled stopper, after the solvent has been allowed to evaporate, the rubber tends to revert to its original form, and thus exerts a considerable pressure on the metal rod. In this way a much tighter joint is obtained than if the rubber stopper were originally perforated to a diameter through which the rod can be forced without pre-swelling the stopper.

Applicants have found furthermore that the Joint so obtained between the riser and stopper remains perfectly tight under all operating conditions.

Since water has the tendency to "wet" the surface of rubber, and since the majority of electrolytes used in wet electrolytic condensers contain water to a greater or lesser extent, it is preferable to add to the solvent used to swell up the rubber, a water-repellent agent. Such a water-repellent agent may be aluminum oleate or similar compounds which are soluble in the swelling agent.

For example if the anode riser, as stated, has a diameter of .125 inch, the stopper 2! is perforated by drilling therethrough a hole with a drill between #50 and #60 (diameters .070 inch to .040 inch). To obtain the desired results it is essentialthat the hole be absolutely clean-cut.

The perforated stopper is then placed into a suitable solvent, for example benzeneto which a water-repellent agent, such as aluminum oleate, may be added in a quantity of 55% to 2% by weight-and left therein for a time period of several hours, the exact time depending primarily on the grade of rubber, the dimensions of the stopper and the hole drilled. and on the solvent. The hole will open to an extent that the riser can be pushed therethrough with comparative ease and without any tearing of the stopper. Thereafter the solvent is caused to evaporate from the plug. The evaporation may be carried on at room temperature or may be accelerated by placing the assembly in a. heated air blast.

When the evaporation of the solvent has been completed, the plug 20, with the anode riser passing through the same, is inserted into the sleeve portion 2|; the plug 20 should preferably be of such a length as to extend on both sides of the neck portion 2 l. Proper sealing between the plug 25 and the neck 2| may be obtained by a fluting operation such as described in the U. 8. Patent No. 1,996,982 to Robert C. Sprague et al.

The electrolytes used in the condensers comprise as a rule, salts, acids, or alkalies and a solvent. Preferably, a combination of a weak acid and a salt is used, for instance, an electrolyte comprising borax and boric acid or ammonium borate and boric acid. However, various other acids and salts either alone or in combination give good results. For instance, phosphoric acid, citric acid, tartaric acid, and/or their salts are also suitable for electrolytes, whereby the salts do not need to be those of the acid used.

The viscosity of the electrolyte may range from that of water at C. to that of a paste.

The invention is also of great utility when the electrical outside connection is made by means of comparatively small diameter wires, instead of rods as above described. To get good results blank and single strand (solid) wires should be used.

While we have described our invention with specific examples and in specific applications. it should be well understood that we do not wish to be limited thereto, but desire the appended claim to be construed as broadly as permissible in view of the prior art.

What we claim is:

In the manufacture of electrical condensers comprising a metal container, an electrode disposed in said container, and a terminal member secured to said electrode and protruding from an opening of said container, the method of providing an hermetically tight seal between said member and the container comprising the steps, providing in a flexible vulcanized rubber member a hole which is smaller in cross-section than the terminal member, swelling the rubber member in a volatile rubber solvent containing 0.5% to 2% by weight of aluminum oleate to increase by at least a factor of 2 the cross-section of said hole, disposing the terminal in the hole so enlarged, evaporating the solvent from the rubber member, disposing the rubber member in the opening of said container and crimping said container about said member.

PRESTON ROBINSON MA'I'HE W NAZZE W SKI. 

